Ethan BrooksBy Ethan Brooks

Updated November 2026

The best energy gels for ultra runners are the ones your gut tolerates at the dose you need, delivering roughly 60 to 90 grams of carbohydrate per hour from a mix of glucose and fructose. Ultra distances stretch fueling across many hours, so the right gel depends on carb type, caffeine content, and how well you have trained your stomach to handle it. Choose based on tolerance first, then flavor and packaging.

Why ultra runners need a different kind of gel

A marathon can be fueled largely from glycogen stored in the body, with a modest intake of carbohydrate during the race. Ultras run long enough that glycogen depletion becomes the limiting factor, and the gut has to absorb fuel continuously while the legs keep moving. A gel that works for a 2-hour race may cause bloating or cramping when you are still going at hour 9.

Shopping for one? See our guide: 6 Best Energy Gels for Ultra Running: Our Picks Compared (2026).

The main difference is absorption capacity. The small intestine can absorb glucose through one transporter and fructose through another. Using both types together raises the ceiling on how much carbohydrate you can process per hour. Many gels combine maltodextrin (a glucose polymer) with fructose in ratios such as 2:1 or 1:0.8 glucose to fructose, which is one reason labels matter more than marketing.

Factors that decide which gel fits you

Several variables determine whether a gel will work over a long day on the trail:

  • Carbohydrate per serving. Most gels provide roughly 20 to 30 grams. Hitting 60 grams an hour can mean two gels, which affects how many you need to carry.
  • Carb source. Glucose-only gels are often easier on the stomach at lower doses. Mixed glucose and fructose gels suit higher hourly intakes.
  • Sodium and electrolytes. Long efforts cause sweat losses. Some gels include sodium; others expect you to pair them with salt tabs or an electrolyte drink. Check whether your race or your sweat rate calls for extra sodium.
  • Caffeine. Caffeine can help in the final hours, but it can also disturb sleep during multi-day events and irritate some stomachs. Caffeine-free options are common and worth considering for night sections.
  • Texture and viscosity. Thin gels are easier to swallow with little water. Thicker gels can sit heavily when your mouth is dry and your pace has slowed.
  • Ingredients. Some runners avoid artificial sweeteners, dyes, or gluten. Read the label rather than assuming a category, since “natural” does not always mean lower in sugar or easier to digest.

How to choose and test a gel before race day

The most common ultra fueling mistake is trying a new gel for the first time on race morning. Gut tolerance is trainable, but it takes weeks. Use your long training runs to find the brand, flavor, and dose that sits well at your pace. Keep a simple log of what you ate, how many grams of carbohydrate it provided, and how your stomach felt at each hour.

Plan for a range of intakes rather than a single number. In hot weather or at high effort, you may need more carbohydrate and more water. In cooler conditions or on steep climbs where you are slower, you may take in less. Many runners set an alarm every 20 to 30 minutes to remind themselves to eat, since hunger signals arrive late in long efforts.

Practical steps for fueling with gels

  1. Calculate your target carbohydrate intake per hour, usually 30 to 60 grams early on and up to 60 to 90 grams for experienced athletes using mixed carb sources.
  2. Divide that number by the carbs per gel to find how many gels you need per hour. Round to a practical number you can actually carry and consume.
  3. Take gels with water, not dry. Sipping a few ounces at each gel helps the stomach process the concentrated sugar.
  4. Start fueling early, within the first hour, rather than waiting until you feel depleted. Recovering from a bonk takes far longer than preventing one.
  5. Rotate fuel types across the day if you tire of one flavor. Some runners alternate gels with chews, real food, or drink mix to reduce flavor fatigue.
  6. Carry a backup plan. Races occasionally lack the brand you trained with, so know a substitute that uses similar carb ratios.

What we’d use

Ultra runners tend to favor gels built around mixed carbohydrate sources and easy-to-swallow textures. Here are product types worth searching for:

  • A mixed glucose and fructose gel for high hourly carbohydrate intake, such as the Maurten Gel 100 or SiS Beta Fuel style products designed for sustained efforts. View on Amazon
  • A caffeine-free gel for night sections or runners sensitive to stimulants. View on Amazon
  • A sodium-enhanced gel or electrolyte companion for hot-weather or high-sweat races. View on Amazon

Read each label for carbohydrate per serving and sodium before buying, since formulas change between versions.

How many gels should an ultra runner take per hour?

Most ultra runners aim for 30 to 60 grams of carbohydrate per hour, and experienced athletes using mixed carb sources can go higher. Divide that target by the carbs in one gel to get the number of gels per hour.

Should I take gels with water?

Yes. Taking gels with a few ounces of water helps your stomach digest the concentrated sugar and reduces the chance of cramping or nausea.

Can I train my stomach to handle more gel?

Gut tolerance improves with practice. Using gels during long training runs, and gradually increasing the carbohydrate per hour, helps your digestive system adapt over several weeks.

Are caffeine gels good for ultras?

They can help in the late stages of a long race, but caffeine may disrupt sleep during multi-day events. Use caffeine strategically and test it in training first.

When should I start taking gels in an ultra?

Start within the first hour rather than waiting for fatigue. Early fueling is easier to maintain than trying to recover once your energy has dropped.

Gut and fueling needs vary widely between individuals. If you have digestive conditions or diabetes, consult a doctor or a registered dietitian before changing your race nutrition plan.

Ready to choose one?

Ethan Brooks

About Ethan Brooks

Ethan Brooks is part of our editorial team and reviews and edits our marathon & half-marathon guides, checking product details against manufacturer specifications and owner feedback.